<div xmlns:c="http://java.sun.com/jstl/core">
    <c:choose>
        <c:when test="#{not empty compute.radius}">
            Radius is not empty: #{compute.radius}.
        </c:when>
        <c:when test="#{empty compute.radius}">
            Radius is empty
         </c:when>
    </c:choose>
</div>